The present invention relates to a virtualization controller, an access path control method, and a computer system. More particularly, it relates to a virtualization controller which connects a host computer and a plurality of storages by a path and provides the host computer with the plurality of storages as virtual N units of storages, an access path control method of the virtualization controller, and a computer system.
As a conventional art that has achieved an enhancement of performance for accessing to a storage system, for example, a technique described in Japanese Patent Application Laid-Open Publication No. Hei 5-12077 is known which will be referred to as “Patent Document 1” hereinafter. This conventional art discloses that a storage system comprises a plurality of storages each has different accessing speed, and according to an accessing frequency to each of the plurality of storages, relocation is automatically carried out between a high-speed accessible storage and a low-speed accessible storage.
The above described conventional art comprises a storage medium which stores data, and a controller which carries out an overall control (for example, data transfer control between a host computer and a storage medium) utilizing the storage medium as a storage, and it is configured such that the host computer and the storage medium are connected via one access path. However, in the foregoing conventional art, there is no consideration regarding a selection of optimum access path, out of the plurality of access paths provided in the controller. Therefore, there is a problem that it is difficult to achieve a performance enhancement in accessing the storage. That is, in the foregoing conventional art, when a plurality of access paths are provided by the controller as access path between the host computer and the storage, for example, there is not disclosed a technique regarding the access performance enhancement by optimizing the access path, considering a usage rate of various resources existing on the access path.
Further, according to the foregoing conventional art, a performance enhancement has been achieved in accessing the storage system which is configured with a plurality of storages each having different access speed, by carrying out optimization (optimal allocation of stored data) of the storage which stores data, according to access frequency to each of the plurality of storages in the storage system. However, in this conventional art, a dada migration (relocation) process between the storages is necessary so as to enhance the access performance of the storage system, and during this data migration process, an access request from the host computer is suspended temporarily in the storage or the access request is processed simultaneously with the data migration process. Therefore, there is a problem that the access performance is remarkably deteriorated.